Volcanoes are holes in the Earth from which molten rock, gas and ash erupt. Magma is the name for molten rock mixed up with gas and sometimes gas bubbles, whilst it is still under the ground. Lava is the name for when it breaks through the Earth’s surface, and you probably know this already, but lava is seriously hot. When we talk about erupt it means to burst out in a rather dramatic way!
The Earth’s surface, called the crust, is made up of huge slabs called plates. They fit together like a jigsaw puzzle. When these plates move and crash against each other the one that slides underneath is pushed down and magma squeezes up between them and rises to the surface of the earth. This then makes bubbles of gas which can cause pressure to build up and eventually explode.
Think about it like this. Do you have a pressure cooker at home? Well if you do volcanoes are like the valves on a pressure cooker and when they erupt, they release the pressure that has built up inside the Earth. Not all volcanoes form this way, some form in areas inside the Earth that have very hot rock. These are called mantle plumes.
The word volcano comes from the name of the Roman god of fire, Vulcan. About 16,000 people from a city called Pompeii in Italy were killed in 79 AD by an erupting volcano called Vesuvius, only one day after their religious festival to Vulcan. This is amazing! The city stayed buried under ash for almost 2,000 years until archaeologists, who are people that learn about ancient things, discovered it. They even found bread in the ovens and 1000s of people were mummified in the temples. Vesuvius last erupted in 1944 and is said to be one of the most dangerous volcanoes in the world because there are so many people living near it in that area. Well then that’s probably not the place to move to!
There are about 1,510 volcanoes that have erupted in the last 10,000 years. Most of them though that are active, are deep under the sea where it’s impossible to measure. So it’s difficult to actually know how many volcanoes there really are on earth. No one is entirely sure, but it is thought that if you include the ones under the sea there are probably about 6,000 volcanoes that have erupted in the world in the past 10,000 years. Wow that’s quite a lot.
Earth has some very big volcanoes like Tamu Massif at the bottom of the Pacific Ocean and Hawaii’s Mauna Loa volcano, which is 5.6 miles (9 kilometers) high. The biggest known volcano in our solar system is Olympus Mars, on Mars. It measures 373 miles (600 kilometers) wide and 13 miles (21 kilometers) high. That is enormous! About half of the world’s volcanoes are found in a horseshoe shape in the Pacific Ocean basin called the Ring of Fire. There are also some under the ice-caps in Iceland.
Volcanoes are all different shapes and the shape depends on what the magma is made of and how it erupts out the earth. For example if the magma is very sticky, it is likely to build up round the volcano and forms the most commonly known Cinder Cone shape, but if the lava is very fluid and flows a long way before it cools, then it makes what’s called a Shield volcano. Other types of volcano are Composite and Lava Domes.
In a word, yes they can. They can trigger Tsunamis, floods, earthquakes, mudflows and rock falls. Buildings can be destroyed, flight paths disrupted, poisonous gases can kill people and animals, ash can ruin crops, dust can result in death or illness and dark skies with heavy winds and rain can occur months after an eruption.
Some nice things about volcanoes is that they produce rich, fertile soil for growing crops and a unique volcanic rock called Pumice which can float in water. You might see your mom using a pumice stone to remove some dry skin!
Now you know all there is to know on volcanoes! Hope you found it interesting.